Mechanistic study of Mg-Mn-Al extrusion alloy with superior ductility and high strength

Abstract

Because of the special crystallization structure (hexagonal close-packed structure), it is difficult to achieve the synergy between strength and ductility in Mg alloys. High strength can be obtained through alloying addition or low-temperature deformation, but these methods usually cause the extremely poor ductility (less than 5%). Meanwhile, solid solution treatment or considerable alloying addition, such as RE, Li, can probably possess the superior ductility, whereas these techniques commonly result in the insufficient strength (poor than 100 MPa). However, Mg 1Mn binary alloy developed in our previous work extruded at a low temperature exhibiting the superior ductility (38.8%) with medium yield strength (204.3 MPa) has been recommended as one of the candidates to improve the strength-ductility synergy in Mg alloys. In this paper, a low-alloyed Mg-1Mn-1Al alloy has been developed to overcome the disequilibrium between strength and ductility. The alloy has a superior elongation capacity (~ 32%) and a reasonably high tensile yield strength (~ 280 MPa) at room temperature. The reasonably high yield strength of the alloy can be dominantly attributed to the refined DRXed grains based on the Hall-Petch relationship, intensified basal texture leading to the basal slip activity difficultly, a great number of nano-scaled Al 8 Mn 5 secondary particles pinning the dislocation motion through the dispersion hardening and the multi-heterogeneous microstructure inducing bask-stress strengthening as dislocation pile-up. The superior elongation capacity of the alloy can be mainly explained as the ultra-fined microstructure through reducing the critical resolved shear stress (CRSS) ratio between prismatic slip and basal slip that favors prismatic slip activity to accommodate basal slip. • Extremely refined Mg-1Mn-1Al alloy is fabricated through the low-temperature extrusion process. • Al addition significantly affects the texture and mechanical properties of Mg-1Mn alloy. • Mg-1Mn-1Al extrusion alloy shows a superior elongation capacity (~ 32%) and a reasonably high tensile yield strength (~ 280 MPa).